Solvothermal-Etching Process Induced Ti-Doped Fe₂O₃ Thin Film with Low Turn-On Voltage for Water Splitting

Abstract

In this work, a thinning process of hematite film accompanied by simultaneous titanium (Ti) doping has been demonstrated. Ti(4+) ion was incorporated into ultrathin Fe2O3 film by solvothermally etching a hematite film fabricated on titanium nanorod array substrate. As a consequence, the onset potential (Von) of oxygen evolution reaction for final ultrathin Ti-doped Fe2O3 film shifted toward cathodic substantially, a very low Von of 0.48 VRHE was realized, approximately 0.53 V cathodic shift of the hematite film. Working mechanisms were investigated from both kinetic and thermodynamic ways. The ultrathin Ti-doped Fe2O3 film exhibited reduced Tafel slope and higher generated photovoltage than the pristine Fe2O3 electrode. Moreover, the highly doped Fe2O3 resulted in significant reduction of charge-transfer resistance at the Fe2O3∥electrolyte interface. The drastic cathodic-shift Von is believed to be a result of combined factors including thermodynamic contribution, improved surface reaction kinetics, as well as facilitated charge transfer across bulk and interface.

Key Strategies to Advance the Photoelectrochemical Water Splitting Performance of α‐Fe2O3 Photoanode

“…The impurity doping is probably the most common method of modification of photocatalytic semiconductors ,,. The introduction of dopant atoms into the lattice of the semiconductors improves their electronic properties and band structure to ultimately enhance their performance of photocatalysis.…”

“…The impurity doping is probably the most common method of modification of photocatalytic semiconductors. [28,34,[49][50][51][52][53][54][55][56][57][58] The introduction of dopant atoms into the lattice of the semiconductors improves their electronic properties and band structure to ultimately enhance their performance of photocatalysis. In case of n-type α-Fe 2 O 3 , either n-type doping (IV-VI metal ions) or p-type doping (I or II metal ions) is needed to supplement its low electron mobility (10 À 2 cm 2 V À 1 s À 1 ), carrier density (10 18 cm 3 ) and electrical conductivity (~10 À 14 Ω À 1 cm À 1 ).…”

Energy level engineering in transition-metal doped spinel-structured nanosheets for efficient overall water splitting

“…12 Recently, metal oxides (MOx; M = Ni, Co, Zn, Cu, Fe, Mn) as electrocatalysts have attracted great interest for water splitting due to their efficient adsorption towards reaction intermediates. [13][14][15] To break their confined sluggish kinetics for water splitting, the nanostructure and composition of MOxbased catalysts should be optimized to expose the largest extent active sites. For example, an abundance of novel nanostructures have been put forward, such as Co3O4/NiCo2O4 double-shelled nanocages, 16 hierarchical NiCo2O4 hollow microcuboids, 17 cobalt(II) oxide nanorods, 18 and ultrathin spinel-structured nanosheets.…”

Surface sulfurization activating hematite nanorods for efficient photoelectrochemical water splitting

“…As compared to the bare a-Fe 2 O 3 photoanodes, all the surface sulfurized a-Fe 2 O 3 nanorod photoanodes show reduced bulk charge transfer resistance (R 1 ), indicating the improved bulk charge transfer process, which should be benefited from the improved electrical conductivity due to the increased carrier density, as evidenced by the MÀS and XAS results. Furthermore, the decreased interface charge transfer resistance (R 2 ) and the increased Helmholtz capacitance (CPE 2 ) reveal the promoted charge transfer processes through the electrode/electrolyte interface for the accelerated water oxidation kinetics [56], as induced by the effective surface sulfurization modification. It could be thus assumed that the efficient charge transfer process at the electrode/electrolyte interface largely determines the improved PEC performances of the surface sulfurized a-Fe 2 O 3 nanorod photoanodes.…”